Set it up in ten minutes
Everything from a first COD surcharge to the filter reference. If the answer isn't here, it's a gap in the docs — tell me and it gets written.
Start here
Four pages cover most installs.
How the amount is calculated
Fixed plus percentage, what the percentage is based on, and how min/max caps interact with tax.
Install & activate Pro
Buy, download and activate, what counts as a site, moving a licence, and what changes when one expires.
Your first fee
Switch a method on, enter the amount, name the fee, save. Ten minutes, free version.
Upgrading from 2.x
What migrates, what changed in the fee maths, and what to check on a store with mixed tax classes.
Recipes
Common setups, written out end to end.
Developer reference
Every woocommerce_pay4pay_* filter, the order-item meta keys, and the REST route — with the signatures unchanged since 2.x.
Still stuck?
Free plugin: the WordPress.org forum. Pro: write to me directly from the plugin's settings screen and you'll get an answer from the person who wrote the code.